Monday, June 24, 2013
08 Joint Design Nº 226
To make the plaster ball mold for the 24mm elbow ball joint, I am reusing the clay build-up from the 22mm wrist ball joint. I place the 24mm diameter glass marble that I am using as a pattern in the 22mm hole and use my paring knife to trace a line around the marble. Click on any image to enlarge it.
I try my best to keep the knife blade straight up and down while I am tracing the line.
I trim the clay to the scribed line so the 24mm diameter marble will fit into the clay build-up. I cannot easily draw a parting line on the glass marble.
I cut a 24mm diameter hemisphere in a scrap piece of matte board to use as a template to figure out when I have the marble halfway embedded in the clay build-up. When I push the marble into the hole, it sinks the clay build-up a little bit around the edge of the marble. I add a thin coil of clay around the edge of the marble, in order to fill in where it sinks in. It is important to have the edge of the clay build-up perpendicular to parting line of the marble. I use my paring knife to model the clay coil so that the clay build-up is flat.
I push and pull the marble, and scrape and add clay until the template shows me that the marble is embedded halfway into the clay build-up.
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